This invention related to communicatation network systems and control of communication networks, and particularly to a communication network system using database information.
In designing a communication network having a great number of nodes and links connecting these nodes, effective use is normally made of network resources by allowing a certain extent of blocking communication messages. In order to minimize the blocking in the network using an arbitrary amount of resource, it is necessary to examine the construction of the network and the effective algorithm for the routing.
The design of the network construction or routing has been made on the basis of the traffic demand prediction at the time of constructing the communication equipment.
Recently, however, the traffic of communication messages in the communication network mainly for data other than POTS (Plane Ordinary Telephone Service) has been rapidly increased in the communication network with the development of the information-oriented society. Therefore, it becomes now more difficult than before to predict the traffic demand in the communication network. Particularly in the network such as the private communication network, in which the traffic is greatly dependent on the change of business due to the social conditions and business fluctuations, it is further difficult to design the communication network.
The technique called the dynamic routing has recently been used under this background. In this technique, the traffic in the communication network having three or more communication nodes is always measured and used to dynamically control the theoretical communication network construction to match the traffic at that time. An application of this technique is disclosed in JP-A-61-251261 (laid open on Nov. 8, 1986 and corresponding to U.S. Ser. No. 727,880 filed in the United States on Apr. 26, 1985).
According to this example, the communication traffic is measured every five seconds, and the amount of communication data is also measured every five minutes. Then, the fluctuations of the traffic are estimated from the measured values, and the network construction is dynamically changed by the most suitable routing on the basis of the comparison with the long-term prediction of demand. In other words, to theoretically increase the capacity of the link in which the traffic has the trend to increase contrary to the estimate, the bypaths to other communication nodes are dynamically established. This dynamical routing technique intends to minimize the blocking in the communication network by balancing the loads to the communication nodes and links.
The communication nodes in this communication network are assumed as the circuit switching type nodes. On the contrary, the communication nodes called the ATM (Asynchronous Transfer Mode) type nodes have recently been discussed. In this mode, the real time information such as voice or moving image are exchanged as communication messages by the same method as the packet exchange. In the ATM type communication node, it is also possible to minimize the blocking by the same dynamic routing based on the estimation of traffic as in the above-mentioned conventional example.
In the ATM type communication, however, the communication performance is affected by the traffic because it uses the packet switching type switching technique. In other words, the information passing through the communication node having large traffic are delayed much and, when the traffic fluctuation is large, the delay time is greatly fluctuated.
Since the above-mentioned conventional example intends to minimize the blocking by the use of the technique for balancing the loads to the communication nodes on the basis of the traffic measurement, it does not make any control of the communication performance other than the blocking in the ATM type communication node.
Moreover, in the prior art including the above-mentioned conventional example, the network control is mainly on the basis of the traffic measurement, and does not consider the performance of communication links between the communication nodes. As a result, the effect of deteriorated performance of communication links on the communication performance cannot be avoided except that the defective line is replaced by a spare line upon line failure.